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Recap of Lecture 1 Parallel Comp. Architecture driven by familiar technological and economic forces –application/platform cycle, but focused on the most demanding applications –hardware/software learning curve More attractive than ever because best building block - the microprocessor - is also the fastest BB. History of microprocessor architecture is parallelism –translates area and denisty into performance The Future is higher levels of parallelism –Parallel Architecture concepts apply at many levels –Communication also on exponential curve => Quantitative Engineering approach New Applications More Performance Speedup

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Shared Physical Memory Any processor can directly reference any memory location Any I/O controller - any memory Operating system can run on any processor, or all. – OS uses shared memory to coordinate Communication occurs implicitly as result of loads and stores What about application processes?

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Structured Shared Address Space Add hoc parallelism used in system code Most parallel applications have structured SAS Same program on each processor –shared variable X means the same thing to each thread